Rola naturalnych i antropogenicznych elementów obiegu wody w zlewni miejskiej (Sokołówka) i podmiejskiej (Dzierżązna)

The role of natural and anthropogenic elements in water circulationin urban (Sokolowka) and suburban catchment (Dzierzązna) The article presents conditions of outflow formation in two catchments situated nearby Lodz and monitored by The Department of Hydrology and Water Management at the University of Lodz. The SCS method, which takes into consideration types of soil and cachment area development, was applied for comparison. The area of Uplands of Lodz, composed of post-glacial formations, is characterised by great diversification of the surface sculpture (Fig. 1). The natural characteristics of both (Sokolowka and Dzierzazna) catchments are similar. The element that differs both basins is the area development. In Sokolowka catchment 47% of the land is covered with buildings (Fig. 2), while in Dzierzazna catchment 60% of the area are arable lands (Fig. 3). CN parameter value has been presented on the maps (Fig. 4, 5). Its average value in Sokolowka catchment is 67 and is a bit higher than in Dzierzazna catchment – 59. The highest values of the parameter are recorded in clay-structured or highly urbanised areas. Low CN parameter values are typical of valley beds and sands. The structure of the CN parameter values is various (Fig. 6). The theoretical value of effective rainfall in both catchments has been calculated (Fig. 7). The difference in P e values appears as early as at the rainfall amount above 20 mm. The high water in July 2008 has also been analysed (Fig. 8). Runoff volume, converted into indicatory values, amounted at 2,29 mm in Sokolowka catchment but only 0,22 mm in Dzierzazna catchment.